Zoom lens and image pick-up apparatus using zoom lens

Abstract

A zoom lens composed of plural groups and adapted for changing group spacing or spacings, and includes, in a first group GR 1 fixed during zooming operation, a reflection member M for bending or folding the optical axis substantially by 90 degrees and a negative group at the object side relative to the reflection member M. At the image side of the first group GR 1 , there are at least included a second group GR 2 movable during zooming operation and having negative refractive power, and a light quantity adjustment member ST 1 fixed during zooming operation. Angle of the reflection member M is changed at the time of sinking lens barrel so that the negative group of the first group GR 1 is accommodated into a space thus defined.

1. A zoom lens composed of plural groups and adapted to change group spacing or spacings to thereby perform magnification changing operation,
 the zoom lens comprising: 
 a first group at least including a reflection member for bending or folding the optical axis and a negative subgroup at an object side relative to the reflection member, said first group being fixed during magnification changing operation; 
 a second group movably provided during magnification changing operation at an image side of the first group and having negative refractive power; and 
 a third group including a positive lens having non-spherical surfaces at both surface sides thereof, and a light quantity adjustment member at the image surface side, the light quantity adjustment member being fixed during magnification changing operation,
 wherein the zoom lens is located within a lens barrel and said negative subgroup undergos a lens barrel sinking operation, and 
 wherein, when the negative subgroup is caused to undergo said lens barrel sinking operation, the reflection member is withdrawn by being rotated with a fulcrum which is not limited to one end side of the reflection member, and the negative subgroup of the first groups is accommodated into a space thus vacated by the withdrawn reflection member. 
 
 
     
     
       2. The zoom lens according to  claim 1 ,
 wherein the negative subgroup of the object side relative to the reflection member of the first group satisfies the following formula (1),
   2.0 <|fa/fw|< 6.0  (1) 
 
 In the above formula, 
 fa: focal length of the negative subgroup of the object side relative to the reflection member of the first group, and 
 fw: focal length at broad angle end. 
 
     
     
       3. An image pick-up device comprising:
 a zoom lens composed of plural groups and adapted to change group spacing or spacings to thereby perform magnification changing operation; and 
 an image pick-up device for converting an optical image which has been formed by the zoom lens into an electric signal, 
 the zoom lens at least including:
 a first group at least including a reflection member for bending or folding the optical axis and a negative subgroup at an object side relative to the reflection member, said first group being fixed during magnification changing operation; 
 a second group movably provided during magnification changing operation at an image side of the first group and having negative refractive power; and 
 a third group including a positive lens having non-spherical surfaces at both surface sides thereof, and a light quantity adjustment member at the image surface side, the light quantity adjustment member being fixed during magnification changing operation,
 wherein the zoom lens is located within a lens barrel and said negative subgroup undergos a lens barrel sinking operation, and 
 wherein, when the negative subgroup is caused to undergo said lens barrel sinking operation, the reflection member is withdrawn by being rotated with a fulcrum which is not limited to one end side of the reflection member so that the negative subgroup of the first group is accommodated into a space thus vacated by the withdrawn reflection member. 
 
 
 
     
     
       4. The image pick-up apparatus according to  claim 3 ,
 wherein the negative subgroup of the object side relative to the reflection member of the first group satisfies the following formula (2),
   2.0 <|fa/fw|< 6.0  (2) 
 
 In the above formula, 
 fa: focal length of the negative subgroup of the object side relative to the reflection member of the first group, and 
 fw: focal length at broad angle end.